JP2633271B2 - Apparatus and method for controlling gas turbine engine - Google Patents

Description

The present invention relates to an engine control system and method for a gas turbine engine.

The fuel control system of the prior art gas turbine engine performs a closed loop operation based on engine parameters such as engine pressure ratio defined by the ratio P ₅ / P ₂ with respect to the engine air inlet total pressure of the engine exhaust pressure (EPR). That is, the desired or reference EPR is calculated based on the throttle setting and ambient air conditions to
It is compared with the EPR, and the fuel supply amount is changed according to the result so as to make the error of the EPR zero. If either the reference EPR or the signal required to calculate the actual EPR cannot be detected, the control action is another control mode, for example the speed N of the low pressure compressor if the engine is a two-shaft gas turbine engine. Forced to be based on _one . In this case, the reference value N ₁ (N _1REF) is calculated based on the atmospheric conditions and the throttle setting. Then, N _1REF is compared with the actual N _1, and the fuel supply amount is changed according to the result so as to make the error between N ₁ and N _1REF zero. However, since the characteristics of these different reference values are different, there is a possibility that the engine speed temporarily changes suddenly when switching the control mode. This is called a "pipe". Pipes not only cause anxiety to the pilots and passengers of the aircraft, but also cause the engine to respond as expected when changing engine operating conditions, such as when the pilot is urgently opening the engine output. Causes dangerous situations.

With the known PW2037 two-shaft engine manufactured by United Technologies Corporation's Pratt & Poitney Division, if such a control mode change occurs, the new reference parameter is adapted to the value of the failed reference parameter at the moment of failure. Is used to remove the bumps. More particularly, EPR is continuously monitoring the value between N ₁ which is N ₁ the main mode have been made the control operation based on EPR when a backup mode, EPR
Use the control mode fails the value of N ₁ of the previous failures in the control, to adapt the value of N _1ref to be equal to the value of the N _1. If EPR control mode (the value of ie adapted N _1ref) desired N ₁ value immediately after the failure Ho value of N ₁ before the failure Isuzu identical bumps are virtually eliminated. This corresponds to a case where the EPR control mode fails while the engine is operating in a steady state or performing a slow acceleration / deceleration operation. On the other hand, if a failure in the EPR control mode occurs when the engine begins to change state significantly, EP
Since the engine speed at the time of the failure of the R control mode greatly differs from the desired engine speed (N _1REF ) corresponding to the new throttle setting position at the time of the failure of the EPR control mode, the bump is not removed. Remains. In response, the fault logic provides overcompensation, resulting in a significant reduction in engine thrust.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an engine which accompanies switching when a control mode of a gas turbine engine is switched from a mode based on a first engine parameter to a mode based on another engine parameter. It is an object of the present invention to provide an engine control system and method with a minimal effect on operation.

Another object of the present invention is to change the control mode of the gas turbine engine from a control mode in which the control mode is controlled as a function of the actual value of one parameter to a control mode in which the control mode is controlled as a function of the composite value of the parameter, so that the influence on the engine operation is minimized. And a fuel control system and method for a gas turbine engine that switches to

SUMMARY OF THE INVENTION In summary, a control system for a gas turbine engine according to the present invention performs control based on a composite value of control parameters when actual measured values of the control parameters become unavailable. When switching the control parameters to the composite parameters, a constant trim is added to the composite parameters so that the control of the engine operation is smoothly switched, so that the composite parameters are measured last among the actual values of the parameters at the time of switching. Is equal to the value. As a result, even if the control mode is switched, the engine operation does not change suddenly. After the switch, the trimmed synthesis parameters are changed by the same amount in response to changes in the untrimmed synthesis parameters.

In effect, the gas turbine engine control system according to the present invention controls the engine as a function of the actual value of a parameter, and based on a function of the composite value of that parameter when the reliable actual value of this parameter becomes unavailable. Switch to control mode. The actual value measured immediately before the actual parameter value disappears is used as the initial value of the parameter composite value at the time of switching, and this initial value is changed by an amount equal to the parameter composite value when it changes.

In the system and method of the present invention, when the actual value of the parameter disappears, a fixed value trim is added to the parameter composite value. This trim has a value such that at the time of the switching the magnitude of the composite value is equal to the magnitude of the last good actual value of the parameter. Thus, even if the control input signal is suddenly switched to the parameter composite value at the moment of the switch, this input signal value does not change from the last measured actual value of the parameter and no sudden change or bump occurs in the engine operation.

Although the preferred embodiment uses compressor speed as a configuration parameter, the present invention is effective in removing any bumps in engine operation associated with switching from actual to composite values of any parameter.

Embodiments The above and other objects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments of the present invention with reference to the accompanying drawings.

In the following description, a two-shaft turbofan gas turbine engine indicated generally by the reference numeral 10 will be considered as one embodiment of the present invention. The engine 10 is disposed between a low-pressure compressor 12 connected via a shaft to a low-pressure turbine 14; a high-pressure compressor 16 connected via a shaft to a high-pressure turbine 18; Combustion section 20. The plurality of fuel nozzles 22 inject fuel into the combustor 24 of the combustion unit 20. The flow rate of the fuel supplied to the nozzle 22 is changed by the valve 26.

An electronic engine controller automatically controls the fuel flow based on pilot requirements (throttle settings), various aircraft and engine parameters, and according to theoretical and empirical relationships established between the various parameters. In this embodiment, the operation of the main control mode at the time of fuel flow control by the electronic engine control device is based on the engine pressure ratio (EPR) defined as the ratio of the engine inlet pressure (P ₂ ) to the engine outlet pressure (P ₅ ). Executed. As shown, a signal 30 representing the signal 28 and the outlet pressure P ₅ representing the inlet pressure P ₂ is supplied to a divider 32. The divider 32 has an engine pressure ratio EP
A signal 34 representing R is output, which is provided to the fuel control section indicated by block 36. This fuel control portion 36 is a planned value of the engine pressure ratio E to be compared with the actual EPR.
Stores PR schedule. The control section 36 sends a signal 38 to the fuel nozzle valve 26 to control the fuel flow and change the engine speed so that the actual EPR matches the EPR schedule corresponding to the current throttle setting.

If the primary fuel control parameter, EPR, or the EPR schedule becomes unavailable or unreliable (hereinafter such a condition is referred to as an EPR mode failure), the control unit 36 controls the fuel flow rate control using the secondary fuel control parameter. It switched to control based on certain low-pressure side compressor speed N _1. Referring to the drawing, the control section 40 continuously generates a scheduled output signal 42 representing the low-side compressor reference speed plan value _N1REF . This reference speed is the maximum speed allowed by the engine under the current conditions and current throttle settings. Actual signal 44 representing the speed N ₁ of the low-pressure compressor is subtracted from N _1ref in the subtracter 46, signal 48 representing the obtained difference is supplied to the switch 50. Of course the engine is still in a state of being controlled based on EPR, N ₁ is a function of the EPR than EPR schedules incorporated in the control section.

A signal 52 is provided to switch 50 when an EPR mode failure occurs. If the signal 52 is not present, the output 53 of the switch 50 becomes the value calculated at each point of the signal 48 and is supplied to the row selection gate 54. On the other hand, when the signal 52 is supplied to the switch 50, the output signal 53 of the switch 50 becomes a signal 56 corresponding to the calculated value of the signal 48 immediately before the signal 52 is supplied to the switch 50. Thereafter, the value of the signal 48 at this time is continuously supplied to the row selection gate 54.

The function generator 58 is a signal 60 representing the Mach number _{Mn of the} aircraft.
And signal 6 from the control section 36 representing the EPR schedule
1 is supplied continuously. Function generator 58 generates a signal 62 representative of the low pressure compressor speed corrected for low compressor inlet temperature on the basis of these input signals (N _E C _2). As is well known in the art of the present invention, a signal 62 representing the corrected low pressure compressor speed and an appropriate multiplier signal 64 (a function of the low pressure compressor inlet temperature) are provided to a multiplier 66 to provide a low pressure rotor speed ( A signal 68 representing an estimate of N _E ) is obtained. The estimated speed signal 68 of the low-pressure side rotor is N
_The difference signal 72 obtained by subtracting from _1REF is supplied to the switch 74.

A signal 76 is provided to switch 74 when an EPR mode failure occurs. When the signal 76 is not present, the switch 74 passes the calculated value of the signal 72 at each time as it is. On the other hand, when the signal 76 is supplied, the output signal 78 of the switch 74 is a signal representing the calculated value of the signal 72 immediately before the switch 74 is supplied with the signal 76.
Equals 80. That is, the value of signal 78 is N _1REF and EPR
It represents the difference from the low-pressure rotor speed estimated based on the schedule and the current engine throttle setting. Estimates of the low-pressure rotor speed is not based on the low-pressure rotor speed N ₁ at each time point. Therefore, the signal 68 representing the estimated compressor speed N _E even if the EPR schedule can no longer disabled or reliable use before and engine immediately move the throttle is changed from the previous speed to a new speed to the new throttle setting It is approximately equal to the speed used in the corresponding EPR schedule. In contrast, speed signal 44 is the actual engine speed in the event of an EPR mode failure, which is significantly different from the desired speed based on throttle settings and EPR schedule.

The speed difference signals 78 and 53 are both supplied to the low selection gate 54, and the lower signal of the two signals is selected as the output signal 82 and supplied to the high selection gate 84. The high select gate 84 is supplied with a signal 86 in addition to the signal 82. This signal 86 is always zero. Thus, if the signal 82 is negative, the output signal 88 of the high select gate 84 will be zero. Otherwise, the value of signal 88 is equal to the value of signal 82. By providing the high select gate 84, the signal 88 ( _N1REF trim) is prevented from becoming negative. Negative signal 88 occurs when an EPR mode failure occurs during deceleration.
The value of the signal 92 when the signal 88 becomes negative is larger than N _1REF, N _1REF the situation according for the maximum speed of the low pressure compressor acceptable upon safe operation of the engine must be avoided. As a result, only negative trim is added to _N1REF .

The value of signal 88 is subtracted from N 1 _{REF into} a subtractor 90, and the resulting difference signal 92 is provided to a subtractor 94 along with a signal 44 representing the current actual low side compressor speed. Signal 92 representing the difference between the actual engine speed N ₁ and the desired engine speed thus obtained is supplied to the control portion 36. EPR signal 34 or E stored in control section 36
If the PR schedule becomes unavailable or unreliable, the control section 36 controls the valve 26 to change the fuel flow such that the error signal 96 becomes zero.

To avoid "bumps" in the engine operating at steady state, the trim limit mechanism of the control system must not affect the trim operation if an EPR mode failure occurs during steady state operation of the engine . This is guaranteed if the value of signal 68 is always smaller than the value of the compressor speed corresponding to the throttle setting in EPR mode. Accordingly, as the Mach number curve used with the function generator 58 never exceeds the rate at which N _E is designated by the EPR schedule when EPR mode failure has occurred, preferably selected it than to slightly become small Is done.

In this embodiment, the main parameter is set to EPR.
Of course, the present invention can be applied to a case where a main parameter other than PR (for example, a fan pressure ratio or a weighted fan / engine pressure ratio) is used.

It is known that if some of the parameters required by the control system in operating the engine fail, a composite value is calculated and used instead of the measured value of that parameter. For example, the combustion chamber pressure is owned by the present applicant, David M. Newworth et al., U.S. Patent No. 4,212,161
It is possible to synthesize by the number. Preferably used when you can not or if reliable measured value of N ₁ calculated combined value of N ₁ (hereinafter referred to as N _SYN) can not be obtained in the present control system.

When suddenly switching to another control mode, a “bump” may occur when switching from the actually measured value of the parameter to the composite value. The control logic of FIG. 2 illustrates a technique for removing such bumps. Parameter synthesized in the example of Figure 2 is N _1. Combined value of N ₁ is calculated based on the most recent valid information, constantly updated, that measured value of N ₁ is used when you may become unreliable or unavailable (N ₁ fault) at any time it can. Referring to FIG. 2, the Mach number of the aircraft and the high-pressure compressor speed (N ₂ C ₂ ) corrected for temperature at the low-pressure compressor inlet are function generators.
Supplied to 200. The function generator 200 provides an estimate of the low pressure compressor speed corrected for the temperature at the constant pressure compressor inlet (N
_SYN C ₂₎ to output an output signal 202 representing the. The value of signal 202 is determined from an empirically derived relationship based on the steady state operating characteristics of the engine established between the Mach number and the corrected high pressure compressor speed.

As is well known in the art of the present invention, a low pressure compressor speed estimate signal 202 and an appropriate multiplier signal 204 (which is the same as the multiplier for multiplier 64 in FIG. 1) are provided to multiplier 205. As a result, a signal 206 representing an estimated value or a composite value of the low-pressure rotor speed (N 1 _SYN ) is obtained. Signal 206 representing the value of N _1SYN
Is based on an empirical relationship between the high and low pressure rotors during steady state operation of the engine, and the signal 206 is passed through a compensator 208. Engine dynamic characteristics of the correction pressure rotor speed N ₂ C ₂ when undue behavior replaced with the characteristics of the output N _1SYN C _2. In the steady state, the compensator 208 does not operate. Such compensators are well known in the art of the present invention.

N _1SYN output signal output on line 99 from compensator 208
99 is continuously supplied to the subtracter 100 together with the signal 44 representing the measured value of N _1. Signals 99 and 4 output from subtractor 100
The difference signal 102 of 4 is supplied to the switch 104 with signal 106 indicating whether N ₁ has failed (i.e. unreliable or unavailable).

If the signal 106 is N ₁ indicates that it is a normal, the output signal 108 of the switch 104 represents the calculated value of the difference at each time point N ₁ and N _SYN. On the other hand, the output signal 108 case shown that signal 106 is N ₁ is defective in the signal 110 indicating the calculated value of the difference between N ₁ and N _SYN immediately before the signal telling the failure to switch 104 is supplied Become equal. In any case, the output signal 108 of the switch 104 is sent to the subtractor 112 together with the signal 99 representing N 1 _SYN, and the output signal 114 of the subtractor 112 is sent to another switch 116 together with the signal 44 representing the actual measured value of N ₁ .

The failure indication signal 106 is also supplied to the switch 116.
Signal 106 is a signal 44 representing the N ₁ if indicates that N ₁ is normal is output as the output signal 118 passes through switch 116. If on the other hand N ₁ defective signal 118 takes the same value as the signal 114 representing the estimated value of N _1. In the preferred embodiment, signal 118 replaces signal 44 provided to subtractor 94 in FIG.

The value of the output signal 114 in accordance with the present invention the moment that N ₁ fails (i.e. the moment of switching to the use of N _SYN) is, and the value of the signal 118 with the also obtained just before the substantially failure It is equal to the normal measurements of N ₁ was. As a result, no bumps occur at the moment of switching and the engine is N _1SYN
Is controlled continuously as a function of

The method for removing bumps when switching from the actual engine speed to the composite engine speed described above is used when switching control parameters from engine control using an arbitrary measured parameter to engine control using a composite value of the parameter. It is clear that is also effective.

Various modifications and omissions are possible within the spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a two-shaft gas turbine engine using a control device according to the present invention, and FIG. 2 is a diagram showing another embodiment of the control device of the present invention. 10 gas turbine engine, 12 low-pressure compressor, 14 low-pressure turbine, 16 high-pressure compressor, 18 high-pressure turbine, 20 combustion section, 22 fuel nozzle, 24 combustion chamber, 26 fuel nozzle valve, 28 ... P ₂ signal, 30 ... P ₅ signals, 32 ... divider, 34 ... EPR signal, 36, 40 ... control part, 38,53,56,78,80,82,86,88,92,10
2,106,108,110,114,118,202,204,206 ... signal, 42 ... N _1REF
Signal, 44 ... N ₁ signal, 46,70,90,94,100,112 ... subtractor, 48,
72 ... difference signal, 50, 74, 104, 116 ... switch, 52, 76 ... EPR mode failure signal, 54, 84 ... gate, 58,200 ... function generator, 6
0 ... Mach number signal, 61 ... EPR schedule signal, 62 ... N _E C ₂
Signal, 64 ... multiplier signal, 66,205 ... multiplier, 68 ... N _E signal, 96
... error signal, 99 ... line, 208 ... compensator.

Claims (5)

(57) [Claims] 1. A method for controlling the operation of a gas turbine engine as a function of an actual value of a first parameter (N ₁ , 44) and simultaneously calculating a composite value of the first parameter (N _1SYS , 99). A method of controlling a gas turbine engine (10) by a control device that performs an operation of controlling based on a combined value of the first parameter when an actual value of the first parameter becomes unusable: Continuously calculating (100) a trim value (102) defined as the difference between the composite value (99) and the actual value (44) of the first parameter; when the actual value of the first parameter becomes unusable Fixing the trim value to the calculated value before use is disabled (104); after the actual value of the first parameter is disabled, the fixed trim value is continued to the composite value (99) of the first parameter Applied to form a trimmed composite value (114) (11
2); after the actual value of the first parameter becomes unusable, use the trimmed composite value (144) of the first parameter instead of the actual value (44) of the first parameter A method comprising: 2. The method according to claim 1, wherein the composite value of the trimmed first parameter used by the control device is an actual value obtained immediately before the actual value of the first parameter becomes unavailable when the actual value of the first parameter becomes unavailable. 2. The method according to claim 1, wherein the method has equal values. 3. The first parameter is an engine speed (N ₁ ).
And that the trimmed composite value of the engine speed used first when the actual value of the engine speed becomes unavailable has a value equal to the actual value of the engine speed obtained immediately before it became unavailable. The method of claim 1, wherein the method is characterized in that: 4. A gas turbine engine comprising a compressor (12, 16), a combustor (24), a turbine (14, 18), and means for continuously measuring an actual value of a first parameter. Means (200) for controlling the engine as a function of the actual value of the _first parameter (N ₁ ) for controlling operation;
Means for continuously calculating a composite value of the first parameter in case the actual value of the first parameter becomes unusable. Means (100) for continuously calculating a trim value (102) defined as the difference between the composite value (99) of the parameter and the actual value (44); Means for generating a fault signal if not determined; means for receiving the fault signal and fixing a trim value to a calculated value obtained immediately before the fault signal is supplied; and Means (112) for continuously applying the fixed trim value to the composite value of the first parameter after receiving the signal to form a trimmed composite value (114); After being supplied, instead of the actual value (44) of the first parameter Apparatus characterized by comprising more as means for controlling the engine with the trimmed composite value of the first parameter (114). 5. The apparatus according to claim 4, wherein said first parameter is a compressor speed.